Modular differential pressure transmitter/manifold for a fluid conveying pipeline

Claim 1

A transmitter/manifold for connection to a source of differential pressure, comprising: a body having first and second input passageways adapted to be connected to the source of differential pressure, first and second instrument passageways terminating at an instrument for measuring differential pressure integral with the body, and an equalizer passageway having first and second ports, and a third body passageway intersecting the equalizer passageway between the first and second ports; a first valve interposed between the first input passageway, the first instrument passageway and the first port of the equalizer passageway; the first valve having a first selectable "NORMAL" position wherein the first instrument passageway is connected to the first input passageway and the first port of the equalizer passageway is blocked; the first valve having a second selectable "ZERO" position wherein the first instrument passageway is connected to the first port of the equalizer passageway and the first input passageway is blocked; a second valve interposed between the second input passageway, the second instrument passageway and the second port of the equalizer passageway; the second valve having a first selectable "NORMAL" position wherein the second instrument passageway, second input passage-way, and second port of the equalizer passageway are open; the second valve having a second selectable "DEPRESSURIZE" position wherein the second instrument passageway and second port of the equalizer passageway are connected and the second inlet passageway is blocked; the second valve having a third selectable "BLOCKED" position where the second input passageway, the second instrument passageway and the second port of the equalizer passageway are blocked, such that a normal mode is accomplished when both first and second valves are on position "NORMAL", a zero mode is accomplished by moving the first valve to position "ZERO", a depressurizing mode is accomplished by further moving the second valve to its position "DEPRESSURIZE", and then further moving the second valve to the "BLOCKED" position produces an isolation mode which also serves as a calibration mode in that a calibration signal pressure can be introduced through the third body passageway to the equalizer passageway which connects to the instrument via the open first equalizer port and first instrument port.